The HK Mark 23 is unusual in the sense that it’s a polymer-frame build, but it was never commodified like GLOCKs or even other HK pistols because production has always been constricted.

I had a Mark 23 M723001-A5 variant for a couple of years and recently shot another one. HK builds only a few hundred of these every year, and they come in two configurations, one with two 12-round .45 ACP magazines (as tested here) or with two 10-round magazines (723001-A5). The latter can make the package suitable for some capacity-restricted states.

What you’re buying, of course, is a lieferwagen that looks like a handgun. The MK23 is 9.65 inches long, 5.9 inches tall, 1.53 inches thick at its widest point, and weighs 39.4 ounces unloaded with an empty magazine. With ammo, it goes all of 51 ounces; add a suppressor, and you’ve got a biceps-building loaded weight of 62 ounces and a nearly 18-inch-long OAL to slice around corners.

If you’re looking for a size reference, think Desert Eagle. Because of its history, the handgun is designated as a Special Forces offensive handgun weapon system, and it’s probably not in the size range that most people would consider for concealed carry. Think of it as a full-size-plus model.

The MK23 is 9.65 inches long and weighs 39.4 ounces unloaded with an empty magazine. Add a suppressor, and you’ve got a loaded weight of 62 ounces and a nearly 18-inch-long overall length. (Woody for TTAG)

The pistol’s background is storied, which contributes to its aura. Heckler & Koch GmbH, or HK, based in Germany, developed the MK23 Model 0 in 1991, and it would be eventually be adopted by U.S. Special Operations Command, or SOCOM.

According to the manual . . .

On May 1, 1996, the first HK MK23 pistols were delivered to the U.S. Special Operations Command for operational deployment, making the MK23 the first caliber-45 ACP pistol to enter American military service since the venerable Government Model 1911A1.

During testing, MK23 pistols met the most stringent operational and accuracy requirements ever demanded of a combat handgun. Endurance testing demonstrated a service life of more than 30,000 rounds of +P ammunition.

To meet the reliability requirement, the pistol had to demonstrate a minimum of 2,000 mean rounds between stoppages (MRBS) with both M1911 ball and +P ammunition. All pistols exceeded the 2000 MRBS with an average of 6000 MRBS.

In more than 450 accuracy test firings from a precision firing fixture at 25 meters, MK23 pistols far exceeded the government requirement, averaging 1.44 inches, with 65 groups of less than one inch.

The HK Mark 23 I recently tested was a commercial model of the U.S. Government issue MK23 MOD 0 pistol and is available in limited numbers. Designated the “Mark 23,” it’s almost identical to the MK23 MOD 0 pistol, right down to its threaded barrel. The main differences are slide markings (Mark 23 as opposed to MK23) and a barrel manufactured to SAAMI headspace specifications.

I recently saw several listings for new Mark 23s ranging from $1800 to $2165 online and used Mark 23s go for around $1700. Depending on condition, I wouldn’t be afraid of buying one of the used guns at all.

My Mark 23 arrived in a black-plastic clamshell case with four 12-round magazines, instruction manual, pad lock, and extra O-rings. I read and reread the manual, which thoroughly explained the Mark 23 pistol’s operating system. It uses a modified linkless Browning-style short-recoil system to lock and unlock the breech.

From the manual:

The rubber O-ring fits into a groove at the front of the HK Mark 23 barrel. Extras are supplied. (Image courtesy of HK)

Upon firing, the pressure developed by the propellent gas forces the slide and barrel assembly to the rear. After approximately 3mm, the locking block will stop the rearward movement of the barrel as the barrel is pivoted downward due to the engagement of the angled surfaces of the locking block with those located in the recoil spring guide rod. The locking block will disengage from the slide and the slide will continue rearward.

The extractor located in the slide will then extract the fired cartridge case. The ejector located in the frame on the left side of the magazine well will eject the fired case as the slide continues rearward and cocks the hammer and compresses the recoil spring. The slide moves forward, feeding the next cartridge from the magazine into the chamber and locking to the barrel breech.

Out front, according to HK, the captured recoil/buffer spring assembly reduces felt recoil by up to 40%. I believe some of that recoil reduction is due to weight, but it’s very easy to recover from each shot and get back on target.

The gun is smooth to operate, but tight nonetheless, and apparently HK does that by machining parts to tight tolerances and then hand-fitting them. An O-ring, which snaps into a milled groove at the front of the barrel, tightens the barrel’s fit inside the frame once the action locks up.

The O-ring lasts beyond 20,000 rounds and can be replaced by the operator without tools in seconds. Four extras are supplied. The slide release is a large frame-mounted lever on the left side of the gun. It was easy and positive to operate.

The matte black frame is made of fiber-reinforced polymer, and it supports a one-piece machined-steel slide with a corrosion-resistant finish, a frame-mounted de-cocking lever, and separate ambidextrous safety lever.

It can be carried cocked and locked in single-action mode with the safety lever on. When I transported the gun, I was comfortable with one in the pipe, the lever on Safe, and the hammer down for double-action-to-single-action operation.

The DA pull is 11 pounds, and the frame affords a lot of grip leverage, so it’s no big deal to operate the trigger quickly in double action. The 0.375-inch-wide grooved trigger shoe was stageable, with take up and a hard stop just before the single-action shot released.

The magazine release is a paddle-style ambi switch located at the rear of the trigger guard.

The Mark 23’s controls are laid out on the left side of the frame and are easy to manipulate. (Woody for TTAG)

HK notes that a pair of Universal Mounting Grooves located on the front of the Mark 23 frame allow for a variety of accessories to be used with the pistol. HK cautions, however, that “Improperly designed or installed accessories may result in damage to the Mark 23 mounting grooves and/or the Mark 23. Such damage is not covered under warranty. Be certain to use only HKI authorized accessories and follow installation and precautions carefully.”

So, to attach standard accessories, you’ll need to have a Picatinny rail adapter, $128. Such adapters are unusual in that they slide onto the frame grooves and screw into the front of the trigger guard, which accommodates specific MK23 accessories such as the Laser Aiming Module (LAM).

The specs say the HK Mark 23 has a “match grade trigger,” but I wouldn’t call it that. The single-action trigger pull is a predictable 6-pound release, and the group testing shows the gun would shoot, so that seems to be nitpickery. But it’s not a 3.5-pound bullseye trigger. For accuracy testing in single action, a round spur-type hammer was easy and positive to pull back.

In the hand, the Mark 23 feels big, and for smaller-handed shooters, the grip will simply be too much to hold well. Some shooters who handled the Mark 23 liked the recoil impulse from the handgun, but the weight tired them out pretty quickly. That weight is even more pronounced with a can attached, but a suppressor makes the Mark 23 a dream to fire.

For this test, I attached a SilencerCo Osprey 45, $734 at SilencerShop.com. According to Silencer Shop’s data, the SilencerCo Osprey 45 provides shooters a hearing-safe 131.3 dB output with subsonic 45 ACP ammo. It has a black-oxide aluminum shell, stainless-steel internals, weighs 11.1 ounces, and is 8 inches long.

I had to buy a new piston for the Osprey to fit the HK. Many .45-caliber pistols (such as FN) have the 0.578×28 tpi muzzle fitment, and a GLOCK 21 is cut to 16mm LH. The HK Mark 23’s thread pitch is 16mm RH, the piston from SilencerShop.com was $71.

The Osprey comes with a three-pronged tool to remove the piston. To install the piston in the end that attaches to the muzzle, the user slides the piston (a stainless cylinder with spokes on one end) into a spring inside a threaded adapter, which then screws into one end of the suppressor.

The HK Mark 23’s thread pitch is 16mm RH. It required a specialized piston for the Osprey suppressor, which was $71 from SilencerShop.com. (Woody for TTAG)

Installation was simple: With the magazine out of the HK and the action locked open, I unscrewed the thread protector, then held the pistol muzzle at 11 o’clock in front of me and started the Osprey onto the muzzle threads. I then screwed the Osprey down as far as it would go onto the muzzle threads, aligned it with the top of the barrel, and tightened the locking lever.

Here’s a suppressed group using Fiocchi 200-grain JHPs. Recovery shot to shot is smooth and easy. (Woody for TTAG)

At 25 yards suppressed, the HK threw Prvi Partizan 185-grain semi-jacketed hollowpoints into groups as small as 1.25 inches. Suppressed, the HK shot 2.1 inches with Fiocchi 200-grain JHPs and 2.6 inches with Winchester white box 230-grain ball. The extra weight of the suppressor really tamed recoil and made cycling back onto targets smooth and easy.

Here’s an unsuppressed group fired in the Mark 23 using Winchester 230-grain ball. (Woody for TTAG)

The big gun didn’t do quite as well without the can, but it was pretty consistent, registering groups of 2.75, 3.0, and 2.8 inches with the same rounds, respectively. Of course, the suppressor-height sights are tall and easy to see, and the front grooves and adapter would have allowed me to attach a laser for even better sighting quality. The sights are three white dots, with two on the rear blade.

The rear sight is adjustable for windage and elevation, and the front post is fixed, rather than being driftable in a dovetail. If I were to buy another Mark 23, I’d plan to add a laser or red dot because, for me, the sights are a limitation on the gun’s accuracy, despite the long sight radius. When I can target with more visual precision, I can shoot the Mark 23 very well.

So, is the Mark 23 worth buying for the regular buyer who’s not Navy SEAL? Yes. It’s one of the best handguns out there, but you’ll pay for the privilege.

If you don’t believe me, read the buyer comments on various retail sites from people who have purchased one. If you already own one or have owned one, please share your experiences with the TTAG readership in the comments section below.

5 stars for ergonomics for a gun close the size of a deagle with ammo capacity comparable to guns much smaller?

4 stars for a trigger that sounds very middle of the road?

3.5 stars for customizability when you can’t even use ubitquitous pic rail items w/o voiding the warranty?

4.5 overall for an overly large target pistol with a crappy trigger very limited aftermarket support? The fanboi is strong with this one. If this was a 400 dollar taurus I would think you were being generous, compaired to other 2000 dollar pistols this gun seriously under performs.

That’s his grouping. others have done much better. Read up on it, the accuracy potential of this handgun is amazing. I was out at the range last night making head shots on a 15 yard C-zone steel target moved out to 28 yards.
You can’t physically attach any pic rail accessories to the HK proprietary grooves or people would. I think HK means if you Dremel out the grooves and slots to make Pic rails work that is what would void the warranty. Talked to HKUSA this morning and they have no problem with me using the adapter available from HKparts.net to attach Pic rail components – it’s the only way you can realistically do it. Even if you could find an original LAM I believe they are now more expensive than the Mark 23.
DA trigger pull sounds very heavy but is so smooth it’s not a problem. I may weigh my DA and SA pulls but I do not plan on modifying the trigger at all. The SA pull may be listed as heavy but again mine breaks very cleanly.
Finally, there are plenty of accessories for this gun out there from many types of holsters ( I have a belt mounted OWB and a SAS tacticool drop-down leg holster that really works well as it’s a bit of a long pull to get out of your waist mounted holster unless you are 6’2″ or more…
Get a used one.. I did and when it arrived it looked mint – got it off HKpro forum with five mags for around $1,700 and have never regretted it… my credit card regretted it though…
Please don’t be a wet blanket on the fire of fun we are having here…

I don’t doubt it’s a fine gun, and think the reviewer did a commendable job reviewing his pistol. I do think if you assume 3 stars to be average performance, and grade on a price based curve the ratings are grossly off on multiple categories. Name me one pistol you CANT buy a holster for. Are you telling me that you honestly believe the customizability is significantly higher than most pistols? If we make a Glock a 5 star customizability, and a xdm a 3 star, the mk 23 is at best a 2 star, ignoring price entirely.

I’m having a hard time thinking of a 2000 pistol that doesn’t brag on one Inch groups. It’s pretty average for the price range.

The standard over-engineered HK piece of gamer crack. I’d be willing to bet money that all the ones that were delivered to JSOC are still sitting in the armory in brand-new condition. Who in their right mind uses a 1kg handgun?

In other words…MEN..would carry the MK23, we are turning into feminine pansies, did the colonists complain about the musket being heavy, did the GI’s complain about the M1 being heavy? Besides it doesn’t jam, it doesn’t malfunction and if you really look into it you’ll know it has fired with a bullet jammed in the barrel a squib, and continued to function

Yes? Look, superman, even YOU have limits. That limit is clearly not the weight of an M1 or this pistol. However, the weight of the firearm contributes to the weight of the kit, which has a maximum of your limit. You can carry an M1 or an M4 with no problem, yeah? Okay, but once you are at your maximum comfortable operating weight, something has to go. You can either carry less rounds of ammo and the lighter gun or you can carry the heavier gun without the extra ammo. Which is more important?

Chest puffing over how heavy of a gun you can lift doesn’t win wars or gunfights.

Not sure about the rest of y’all, but having been there and done that, weight of the gun it’s self isn’t so much the issue these days. It’s the weight of the body armor, combined with the obscene amount of bullshit the military insists on each soldier carrying. The American soldier from the Iraq war to today, actually carries more weight then any soldier throughout all of human history. Don’t even bother bringing up mideval knights, they were on horseback and had squires to ferry most of their load. The previous generations of soldiers had heavier guns, but far less gear, equipment, body armor, comms, and ammo.

Here’s the thing…. would I rather carry a marginally more reliable pistol or an extra magazine for my rifle? Hm…

The rifle is my primary fighting weapon.
The pistol is my “oh shit, oh shit, oh shit, that was a click, that was a click, fuck fuck fuck fuck” weapon.

As somebody already pointed out to you, combat loads are a zero sum game. Every time you add weight somewhere, you have to lose it somewhere else. A fully loaded Glock 20 or 21 is almost a full pound less weight and will do the exact same job 99.99% of the time. Why wouldn’t I put that pound of carry weight into something more useful than a weapon I will probably never draw and that will work just fine without the extra investment?

As someone who carried this weapon in combat, it is heavy. But the weapons weight was not the problem, it was ammo! I carried 6 mags with me, but less ammo than others. The trade of is it hit like a hammer, and allowed me to protect my patients.

My loaded CZ is about 56oz, I carry it all the time – at least 16 hours a day (IWB), every day, and have for several years. I have a good holster and belt and don’t even notice it – if my pants are on, it’s on as well. I’m no huge guy, either – 5’11”, 165#. It doesn’t bother me (or anyone else) at all.
I feel like most other people have gone soft on glocks. I’ll take my all-steel, hammer-fired, awesome triggered super-accurate advantage with no perceived (by me) disadvantage all day long.
I’m actually glad other people thinks that’s redonculous – if anyone ever becomes aware of my massive advantage, they won’t think it’s so unfair because I earned it, though it’s no trouble to me at all.

“Autocannon”? Are you talking about my 9mm CZ or something else?
Either way, I have a distinct advantage over plastic pistol packing wusses, as evidenced by such extreme denials of the obvious truth.
Tell yourself whatever helps you sleep better at night.

The most unused piece of equipment in the Navy’s armory and no way to comfortably carry one because the holster is huge.
Most teams have 11in barrel 416s with custom features and view handguns as transition weapons if the rifle goes down in close quarters.

Pretty much correct. I hear they get issued and pretty much sit in the cage. By the time you put the matched KAC silencer on it, going to an MP5SD isn’t much more unwieldy and has a stock. The grip is huge, and my large hands can’t correctly address the trigger in double action mode and pushes to the left. The USP45CT or HK45CT (MK24) are more commonly used and fit better while losing only 2 rounds in the mag. There’s few aftermarket parts available, so you can’t customize much beyond the 1913 rail adapter for the unique rail. That said, it has a unique feel when shooting that I find enjoyable.

As somebody with probably over a dozen walthers, I salute you and agree with you.
But as somebody who knew nothing about pistols and started out ~20 years ago by buying and carrying a USP.40c, I would buy a Mk.23 if I had that kind of disposable scratch.
Of course, it would probably have to be AFTER I bought the PPQ.Q5.SF…

Back in the 90s I carried a USP.40 and my partner carried a USP.45. The USP.45 and a SOCOM are basically the same gun with different accessories. I loved my USP and regret letting it go. As for that .45 version, I have smallish hands and had no trouble handling the big pistol. I wouldn’t choose one (thus I carried a .40) but if you had issued me the .45 I wouldn’t have complained.

Both pistols had excellent feel, fit and finish, astounding accuracy and flawless reliability. They were precision machines that put me in mind of a fine watch or precision tool. Truly excellent weapons.

Given that the 23 is a significant upgrade from the UPS, I can only imagine that is is truly a thing to behold .

I had a conversation with Bill Rogers around ’94. He said he had gotten a contract with the Navy to train the SEALs when this thing was adopted. I told him I would rather have a compact shoulder fired weapon any day and I like H&K weapons. Own a couple now and probably a dozen over the years. Bill told me some admiral, who’s area of expertise in small arms was bullseye target, came up with the criteria. HK just built to the specs.

Having shot an MP5 and P90, i’d take them over a pistol for home defense. So easy to shoot in semi-auto. Compared to shooting pistol, pistol requires a lot more training and practice, in my experience. But I live in CA, so I’ll keep practicing pistol.

Oh! Almost forgot. I don’t know if I would put an H&K Mark 23 in the same class as more iconic firearms. I believe it will eventually become a footnote in firearms history. And yeah, I’ve shot one. Against my advice a friend bought one. He bought it NIB when they first became available. We took it to the range a few times. I don’t think he’s shot it in 20 years. Damn things are too big an envelope for the cartridge.

No doubt a fine gun, but…. for the price, I’ll pass. For that much coin, any accomplished pistol Smith could could take a more obtainable pistol and tune to the same results. I’ve personally never cared for any sig I’ve ever spent time with, and there have been many. One example is when a friend had a first run 365 and compared it against a beater Taurus pt111 g2 I had. That Taurus grouped better and never failed vs. the 365 that jammed, dropped mags while firing, and discharged when dropped. Nobody was hurt, but that just cemented my lack of confidence in sig.

Writer said: “When I transported the gun, I was comfortable with one in the pipe, the lever on Safe, and the hammer down for double-action-to-single-action operation”
Neither I or my friend can get our Mark 23’s to be hammer down, round in chamber and safety on “Safe” as the safety lever always goes to red dot “Fire” with the hammer down. The manual does not describe how to do it and I always thought it was because tje 87 pound DA trigger acted as a good safety.
Any special technique you can share?

I own about 30 handguns. The Mark23 was one of the two I have ever sold. Huge, heavy, limited capacity. Accurate and pleasant to shoot for sure. Probably pleasant to carry if you’re of the size to play D1 football if not NFL. To me, it seemed pointless after a few range trips. A suppressed 1911 is just as fun and has a better trigger. A polymer framed 9mm fits anyone but a sasquatch’s hand better while holding 5+ more rounds. A 2011 holds more rounds of .45 with a better trigger. My take… if you want a huge .45 (and you don’t happen to be a trust-funded, slightly out-of-date
mall ninja)… put that $1800 toward an STI or SVI range toy. Or better yet, spend it on ammo and go shoot whatever pistol you already own.

Personally, I can’t WAIT to get my hands on one of these HOLY GRAIL pistols…I LOVE my full size USP .45 and I carry it all the time with no problems…. Sure, it’s heavy, but the reliability and accuracy are worth it to me…
I’ll be trading up to the Mark 23 ASAP…
And most importantly, it’s made in THE FATHERLAND!!!

You can’t really tell the Mk 23 story without telling parts of the Beretta and SIG story, as well. The Beretta 92F was largely the result of a specific SEAL Team urging Beretta to modify a few things with the standard 92 for the unit’s use. Things like moving the magazine release from the butt to the frame, re-shaping the trigger guard…etc. This particular SEAL Team had Beretta 92F’s before the U.S. military ever went to the “M9”. During the testing for the new U.S. standard issue sidearm SIG actually slightly outperformed the Beretta. I was told that it wasn’t chosen because Beretta slightly beat the price point over SIG. The real answer is probably a bit more complicated than that, but Beretta did eventually win . The trials lasted a long time during which life went on in the Teams…until Berettas starting failing in the SEAL Teams. I remember those days well. The Teams had a lot of loyalty to the pistol, but all of that ended when Beretta publicly accused the Teams of routinely firing “hot” ammo through the guns. Not a true statement. The Teams dropped the Beretta and were authorized to purchase an “interim” handgun to fill the bill until the ink was dry on the government standard sidearm contract. The Teams bought SIGs and began a loyalty o that system which persists even still.

It wasn’t too long before Army SOF began to sour on the Beretta. Their problem was that they already had M1911A1’s on their TOA&E. The military being what it is, you can only have one caliber of a particular type of like equipment. Army SOF began to work the issue by conceptualizing an “Offensive Handgun” different in definition and .45 ACP. This was just post Desert Storm. SEAL SIGs had been in inventory for 2-3 years and folks were starting to recall that the P226 was only an “interim” buy. Someone was caught using improper justification for a second purchase of SIGs by Congress. During the dust-up which followed Army SOF approached Navy SOF through Crane with the “Offensive Handgun” concept. The Navy could take the lead on the project and if it came off both the Army and Navy SOF would enjoy a new .45 cal handgun. The “Offensive Handgun” project felt the influences of many opinionated pistoleros. A long list of features was drawn up.

Eventually both Colt and HK submitted Phase One Prototypes for endurance testing. I was actually one of the SEALs who had to fire 30,000 rounds through a Colt and HK pistol over the course of a week in 1994 and document every failure. Not as fun as you might think.

We also took the revamped (Phase Two) prototypes to Rogers’ Shooting School for testing (that was fun) in early 1995. I and several other SEAL Team “bullet heads” went to the testing with malice in our hearts not only for the gun but the very concept of the gun. Our intent was to shoot it better than anyone else and then slam it in the critiques.

The gun grew on us haters. That simple. It was dead accurate, big- yes, but manageable. With a suppressor on it is unlike any other handgun.

It was finally issued around 1996 or so. I used it in winter warfare a lot, for over the beach work and diving. I preferred my SIG for assaults. Later in my career I did a lot more diving and over the beach work. The Mk 23 was awesome at that stuff. It is the best weapon to have in a hide site when lying up with a Team in a concealed position. You can bring it to bear day or night on anyone sneaking up on you. It is accurate even after blowing through your hide site material, the suppressor is pretty quiet and the LAM lets you get away with a lot. I used it and trained many other SEALs to use it very capably. The SEAL Teams that did not dive as much as, say, SDV Teams neglected their Mk 23’s. The Mk 23’s strengths were not as obvious to those guys who weren’t swimming and diving all the time. Last year a message came out to turn in all Mk 23’s to Crane. At least one SDV Team flatly refused. A few other Teams suddenly decided they should keep a “few”. So those at NAVSPECWARCOM who had sent the message in the first place restricted the expenditure of .45 ammo, instead. SDV Teams now have Mk 23s but no ammo allowance. They even ordered S&W 686’s from Crane to outfit their guys because a SIG will not survive a long dive very well. I know of a handful of guys who have taken their issue Mk 23’s overseas since the ammo cut-off because they know they can get the ammo there and have actually carried them in missions far from the water.

If it has a trigger anything like the USP .45 I used to own, no thank you. Has to be one of the worst triggers I have used to date. Spongy an squishy brake, loooooong reset and polymer trigger adds to the horrendous feel. She was reliable but that didn’t come close to overriding that sad excuse for a trigger.

It depends on which USP you had, the expert/elite models typically have the best triggers, followed by the tactical, there were a couple of other configurations on specific models like custom combat, and then the standard USP trigger. The Mark 23 trigger isn’t the same as the USP, maybe closer to the Tactical model in feel but still different.